Photolithography is a fundamental process for the fabrication of semiconductor devices or flat panel displays (FPD). Materials used during the process, however, could cause various defects. For instance, unwanted microparticles may be present in solutions such as a resist solution and an organic solvent. A solution containing dispersive polymers, in particular, is subject to local solidification (or gelation) of those substances with the passage of time, resulting in defects. To reduce the chances of defects, a solution is thus supplied to the dispenser nozzle of a spin coater after the solution is filtered by a filter (see JP-A-62-204877 and JP-A-2008-305980).
To enhance the effect of the filtration by a filter used in a resist supply system, it may be desirable to reduce the speed at which a resist solution passes through the filter (i.e., reduce the filtration rate). However, this method requires a long time for the solution to be dispensed onto a wafer, reducing the throughput of the device. Alternatively, if a filter of a small pore size is used to enhance the effect of the filtration, the filtration rate may decrease, resulting in reduced throughput of the resist supply system. The latter method also limits the selection of usable filters.
Conversely, to increase the throughput of the resist supply system, resist suction and filtration may have to be completed in a short amount of time by using a filter having a relatively large filtration surface. However, this does not necessarily increase the filtration rate because the resist solution may not pass through the entire filtration surface of the filter, flowing only through a less-pressurized section. For the purpose of increasing throughput, it also seems feasible to use two chemical supply systems for a single resist coating device, but this method may not allow the same amount of resist solution to be dispensed all the time due to the structural differences of pumps or the like.